Interior upholstery and panel (both side and instrument) of an automobile are usually synthetic leather formulated from PVC (polyvinyl chloride) compounds blended with various amounts/types of plasticizer. For many reasons, car manufacturers prefer to use minimal amounts of PVC inside their cars. Because of chemical inertness, low density, and low cost, polyolefin (PO) compositions are the natural choice to replace PVC materials. Of course, in terms of soft touch feel and other mechanical properties, one has to balance the softness, flexibility, heat resistance, and flame retardance of these PO compositions. More importantly, the current manufacturers of car upholstery and panels want this type of PO based synthetic leather to be processable in their existing equipment (roll mills and calenders) for producing flexible PVC (fPVC) films. However, most POs, when put on a two-roll mill, tend to form films banded to the back roll (the faster-moving roll) when these films are thinner than about 30 mils (762 microns). This improper banding will prevent thin PO films from conveying continuously from one two-roll mill (or calender) to the others in the forward direction, disrupting the normal manufacturing process.
However, some applications require polymeric materials with a soft touch feel. Addition of mineral oil generally improves the flexibility, workability, or distensibility of POs. They are also added to POs as extender or processing oils. However, oils often do not preserve the optical properties (e.g., color and/or transparency), low odor, or use temperature ranges of POs. In addition, oils typically have high pour points (e.g., above −20° C.), producing little or no improvement in low-temperature properties. If their flash points are sufficiently low (e.g., less than 200° C.), the compound can cause smoking and be lost to the atmosphere during melt processing. Another serious drawback is that all or some of the oil can migrate to the polymer surface and evaporate, resulting in deterioration of properties over time. In this respect, they tend to leach out of the PO and impair food, clothing, and other articles that are in contact with the final article made from the PO composition. They can also cause problems with tackiness or other surface properties of the final article.
Conventional mineral oils, even paraffinic mineral oils, impair the properties of polyolefins, in particular semi-crystalline polyolefins (see WO 01/18109 A1 and Chemical Additives for the Plastics Industry, Radian Corp., 1987, pp. 107-116). Indeed, such compounds are often detrimental to semicrystalline polypropylene, in that they migrate to the surface causing parts to become oily (except at very low concentrations), or they degrade mechanical properties because they fail to depress the glass transition temperature effectively. WO 04/014998 discloses blends of polyolefins with non-functionalized plasticizers that are not mineral oils. In particular, Tables 8, 11, and 21a to 22f describe blends of certain impact copolymers with certain liquids and/or plasticizers, and Tables 23a to 23f describe blends of a certain thermoplastic polyolefin composition with certain liquids and/or plasticizers. These blends however are unsuitable for processing on a roll mill or calender because they do not have the appropriate balance of softness and melting properties.
Plasticized polyolefin compositions and their applications are also described in WO 04/014997 and US 2004/260001. Additional references of interest include: U.S. Pat. No. 4,132,698; U.S. Pat. No. 4,536,537; U.S. Pat. No. 4,774,277; US 2004/034148; WO 98/44041; WO 03/48252; and JP 09-208761.
In particular, US 2008/0045638 discloses hetero-phase polyolefin compositions comprising: a) 30 to 99.7 wt % of a polypropylene-based TPO comprising at least 50 wt % propylene and at least 10 wt % ethylene, b) 0.1 to 20 wt % of one or more non-functionalized plasticizer(s) (NFP), and c) 0.2 to 50 wt % of one or more filler(s); and having, among other things, a flexural modulus of 500 MPa or more.
Further, others have proposed processing of polypropylene based materials on calendering equipment. For example, U.S. Pat. No. 5,439,628 and U.S. Pat. No. 5,820,970 disclose certain films of polypropylene/polyethylene (LLDPE, HDPE, etc) blends prepared using calendering equipment. Likewise, U.S. Pat. No. 6,520,235 discloses PVC calendering where a polypropylene film is applied to the PVC during calendering as a casting sheet.
Thus, there is a need in the art for polyolefin compositions that can run on PVC milling and/or calendering equipment without banding to the faster roll and/or disrupting conveyance to a calender mill. There is also a need in the art for such polyolefin compositions capable of being run on PVC milling and/or calendering equipment that have good optical properties, good scratch resistance, good permanence, and/or low tackiness.
The instant invention meets such needs by providing ternary blends of plastomer, an impact copolymer (ICP), and a plasticizer that exhibit good processability on mills and calenders for producing films with thickness of 30 mils (762 microns) or less.